The present invention relates to a balance with a housing that contains a weighing cell and forms the rear wall and the floor of a weighing compartment. The weighing-load carrier of the balance is held by a cantilever arm of the weighing cell.
Balances of this type serve mainly as analytical balances and are used widely in laboratories.
The German utility model DE-U-299 12 867 discloses a balance with an auxiliary display in addition to the main display for the weighing result. The auxiliary display is mounted on the stationary rear wall of the weighing compartment, inside the draft enclosure, and indicates time and/or temperature and other ambient conditions.
Another balance of relevance to the present invention is described in the German utility model DE-U-92 93 744. It is designed so that electronic measuring elements can be installed on the weighing pan by means of a special auxiliary pan that holds the weighing material to be weighed as well as the measuring element. The auxiliary pan has a connector element with a plug for the measuring element. A height-adjustable stand for the processor unit of the measuring element is set up outside of the balance. The electrical cable between the connector element on the auxiliary pan and the stand is arranged to transfer only horizontal forces.
All of the aforementioned known balances suffer from the drawback that their range of applications is very limited and that they lack the flexibility to be adapted for different tasks.
It is therefore the object of the present invention to propose a balance that is of a compact design but is nevertheless adaptable to a multitude of applications as well as optimized with regard to user ergonomics.
According to the invention, the foregoing objective is realized in a balance with a balance housing that contains a weighing cell and forms the rear wall and the floor of a weighing compartment. The balance has a weighing-load carrier held by a cantilever arm of the weighing cell. Built into the rear wall of the weighing compartment is a holder system that allows a variety of weighing-compartment accessories to be releasably installed at different levels above the floor of the weighing compartment.
The balance according to the invention is distinguished by its compact design. The inventive arrangement offers a multitude of application possibilities, as will be described below through examples. Thus, the balance has the flexibility to be adapted for different kinds of experiments, which can be performed inside the weighing compartment.
In a preferred embodiment of the invention, the holder system contains two vertical grooves running parallel to the rear wall. In a further developed version of the same embodiment, a portion of the rear wall projects into the weighing compartment like a column, where the grooves are arranged in the laterally facing flanks. The holder system has a plurality of identically shaped connector formations for a form-fitting attachment of weighing-compartment accessories that have complementary counterparts to the connector formations.
The holder system is advantageous for a height-adjustable installation of shelves, holders for laboratory devices and/or an indicator unit or an ionizer unit to avoid the build-up of electrostatic charges. Shelves attached to the holder system are useful for substance containers, tools, etc. The holder system is configured so that the laboratory devices and/or an indicator unit can be easily installed as well as removed. Laboratory devices that could be installed include, e.g., dispensing devices for powdery and liquid substances.
Depending on the application, the holder system can also include conductor tracks for an electrical power- or signal connection.
In a further embodiment of the invention in a balance for weighing in a microgram range, the holder system may be used to hold an interior draft-shield enclosure with side walls that can be raised for placing a weighing object on the weighing-load carrier.
The holder system in a preferred embodiment of the invention has a motorized drive mechanism to raise and lower the accessory devices that are attached to the holder system.
In a preferred embodiment of the invention, the cantilever arm of the weighing cell has a coupling arrangement that protrudes into the weighing compartment through passage openings in the rear wall. The weighing-load carrier is releasably attached to the coupling arrangement. In particular, the coupling arrangement is located to the sides of the holder system and/or in alignment with the grooves.
According to a further preferred embodiment, the weighing-load carrier is configured as a plane horizontal grate. This concept offers many application possibilities within the scope of laboratory weighing. For example, containers or accessories of the most diverse kinds can be either set on the grate or clipped to the grate. Spilled weighing material does not stay on the weighing-load carrier, but drops between the bars of the grate, so that the spilled material cannot be inadvertently included in a weighing. In a particularly favorable design, the bars of the grate have a roof-like triangular profile with a ridge on top, which enhances the tendency of spilled material to drop off the weighing-load carrier, so that the potential for weighing errors is reduced even further.
The weighing-load carrier can also be configured as a holder for laboratory vessels. To make the dispensing of substances into the vessels more convenient, the holder can be rotatable to different tilt angles.
A preferred embodiment of the invention has a load-relief mechanism to lift the load off the weighing-load carrier. The load-relief mechanism is arranged at the rear wall and has a lift platform shaped like a grid of bars or spaced-apart lamellae. When the lift platform is raised, the bars or lamellae of the lift platform come up through the gaps between the bars of the weighing-load carrier and lift the weighing object off the carrier grate. With the load-relief mechanism, it is not necessary to remove and subsequently return the weighing load when re-zeroing the balance. Thus, a potential source of weighing errors is avoided. It is also possible to perform long-term weight studies and recalibrate the balance between the individual weighings.
Other advantageous embodiments of the balance according to the invention provide the possibility of integrating code-identification systems or set-ups for experiments into the balance, e.g., for turbidity measurements, to make certain work processes more efficient.
Advantageous traits of a balance according to the invention are its compact design and its modular configuration that make it remarkably versatile for a variety of laboratory applications. The inventive balance is distinguished by its flexibility and by how quickly it can be reconfigured for different applications. In addition, cleaning the separate components is very easy.